Current differential protection method and system for dc power grid
A technology of differential protection and power grid current, which is applied in the direction of automatic disconnection emergency protection devices, emergency protection circuit devices, electrical components, etc., and can solve problems such as slow motion speed, inability to ensure stable operation of the power system, and delayed work of backup protection
Active Publication Date: 2018-06-12
HITACHI ENERGY SWITZERLAND AG
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Problems solved by technology
However, their disadvantages are: the main protection has poor sensitivity to high resistance faults, and may malfunction in the LCC DC grid; while the backup protection has a very slow action speed
[0028] 2) Impact on voltage change rate and low voltage protection
[0031] When the line is connected to the ground through a large impedance, a small DC voltage drop will cause the voltage change rate protection to malfunction
[0032] 3) Impact on current differential protection
[0037] If the fast protection (traveling wave protection) malfunctions, the backup protection will delay the work
And the delay time is too long to ensure the stable operation of the power system
Method used
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[0178] Hereinafter, the present invention will be described in more detail through specific embodiments in conjunction with the accompanying drawings.
[0179] image 3 A flowchart illustrating a method for DC grid current differential protection according to the present invention is shown, the method comprising the following steps:
[0180] Step S301: Obtain the pole voltage sampling value and pole current sampling value in the local terminal and the remote terminal of the DC line;
[0181] Step S302: Calculate the pole voltage value of the fault component according to the pole voltage sampling values of the local terminal and the remote terminal respectively; and calculate the pole current value of the fault component according to the pole current sampling values of the local terminal and the remote terminal respectively;
[0182] Step S303: Based on the Bergeron model (Bergeron model), by calculating the fault component pole voltage value and the fault component pole c...
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A DC grid current differential protection method and system are provided. The method includes: sampling value acquiring step (S301): acquiring pole voltage and current sampling values in local and remote terminal of a DC line; fault component extracting step (S302): calculating fault component pole voltage and current values according to the pole voltage and current sampling values of local and remote terminal respectively; Bergeron model calculating step (S303): acquiring fault component pole current values at selected point on the DC line between the local and the remote terminal, by the calculation of the fault component pole voltage and current values of local and remote terminal calculated in the fault component extracting step, based on Bergeron model; current differential protection judging step (S304): judging internal fault if the fault component pole current values at selected point meet preset current differential protection criterion. Because of adopting Bergeron model, it improves the calculating speed.
Description
technical field [0001] The present application relates to a DC grid current differential protection method and a system thereof. Background technique [0002] In existing HVDC systems, protection based on traveling wave fronts, usually based on local measurements, is used as primary protection, and classical current differential protection is used as backup protection. However, their disadvantages are: the primary protection has poor sensitivity to high-resistance faults, and may malfunction in the LCC DC grid; while the backup protection has a very slow action speed. [0003] In existing two-terminal HVDC systems, the primary protection for transmission lines is mainly based on the rate of change and amplitude of the directional traveling wave front. This type of protection has the obvious advantage that it uses only local measurements and has a very fast action on metal faults. [0004] But one disadvantage of this type of protection is its very low (poor) sensitivity to...
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IPC IPC(8): H02H7/26H02H3/26
CPCH02H7/268G01R31/08H02H7/261H02H7/263H02H7/265
Inventor 刘凯李幼仪王建平
Owner HITACHI ENERGY SWITZERLAND AG